Method of testing automotive distributors



July 10, 1951 P. o. STEWART 2,550,259

METHOD OF TESTING AUTOMOTIVE DISTRIBUTORS Filed April 17, 1951 I To PUMPINVENTOR. PATH/83W a SEW/1R7 AGE/V7 Patented July 10, 1951 UNITED STATESPATENT OFFICE METHOD OF TESTING AUTOMOTIVE DISTRIBUTORS The presentinvention relates to a method of checking the operation of automotivedistributors, more particularly of distributors in which the advance ofthe spark is controlled by vacuumoperated means. This application is acontinuation-in-part of my co-pending application Ser. No. 81,473, filedMarch 15, 1949.

The invention is primarily designed for use with a more recent type ofdistributor system in which the movement of a breaker plate, carryingthe circuit breaker which is operated by a cam mounted on thedistributor shaft, is effected exclusively by a vacuum connection to thecarburetor, in accordance with a predetermined law which in turn is afunction of the tension of a.

pair of control springs. It should be understood, however, that theinvention may be employed with some advantage with any type ofdistributor in which at least part of the displacement of the breakerplate or its equivalent is due, to the application of a variable vacuumtaken from any convenient source, e. g. from th manifold of the motor.

The classical method of checking the performance of a distributor of anykind involves the use of stroboscopic apparatus, the tests being carriedout while the engine driving the, distributor shaft is in motion. Thiscalls, for a rather complicated set-up and precludes the testing ofdistributors by simple means; moreover, the making of necessaryadjustments during tests is rendered diflicult by the fact that theresetting of, the springs must be done in the immediate vicinity of arapidly rotating shaft, unless one decides, to stop the engine beforeeach adjustment.

The general object of th present invention is to provide a method ofchecking the performance of a vacuum-controlled distributor which willavoid the above disadvantages, and which will allow testing adistributor during standstill or when it is disconnected from theengine, all without the use of a spark-generating circuit.

The above and further objects of the invention will become more fullyapparent from the following description of a now preferred embodiment,reference being had to the accompanying drawing in which:

Fig. 1 shows in plan view a distributor of the character set forthabove, in combination with a checking or testing device adapted to carryout the method of the invention;

Fig. 2 is a fragmentary section taken on the line 2-2 of Fig. 1; and

Fig. 3 is a graph used in explaining the method according to theinvention, this graph representing the performance characteristic of thedistributor shown in Fig. 1.

Referring to Figs. 1 and 2, there is shown a conventionalvacuum-controlled distributor Ill of which the cover has been removed.The distributor comprises a housing I I and a breaker plate 12 journaledin this housing, this plate being concentric with a distributor shaft I3passing through the center of the housing. The shaftv is flattened at Mfor the entrainment of the distributor rotor or switch arm (not shown).

The breaker plate I2 carries a U-shaped contact spring l5 one leg ofwhich is clamped in a terminal member I6, the, other leg co -operatingWithv a stationary contact I! likewise mounted on the plate, 12. A wireI8 extends from the terminal member Hi to a condenser l9 from which a.flexible wire 20 leads to a terminal 2| for connection to other circuitelements (not shown) including a spark coil and a source of voltage.These elements need not. be connected to the terminal 2| during the,tests subsequently described. A breaker arm 22, pivoted to the plate l2such manner as periodically to disengage the same from the contact I!when the shaft l3 rotates, the arm 22 being then. intermittentlydeflected by a. hexagonal cam 24. mounted on the shaft. The contact I!is grounded to the distributor housing by way of a flexible wire 35.

The plate I2 is provided withtwo circular cutouts 25, 26 through whichpass respective posts 21,, 28. rising from the bottom of the housing ll,

these postsand cutouts limiting the angular dis.- placement of the plateI 2 relative to the distributor housing. Post 21. serves as oneanchorage for a light coil spring spring being anchored to an eccentricstud 30 projecting froma pin 3| which is rotatably held in the plate 12.Post 28 serves as one anchorage for a heavy coil spring 32, the otherend of this spring being anchored to an eccentric stud 33 projectingfrom a pin 34 which is also rotatably held in the plate l2. It will beunderstood that rotation of the pins 3|, 34 will permit adjustment ofthe tension of springs 29, 32 in the home position of the plate [2,which is the position illustrated in Fig. 1.

The mechanism for angularly displacing the breaker plate I2 with respectto the housing ll includes a suitable connection, not shown, betweenthis plate and a diaphragm 36 inserted between a tube 31, extending fromthe housing II, and a nipple 38. The apparatus so far described isentirely conventional, nipple 38 being norat 23, bears upon the contactspring 15 in.v

29, the other end of this.

mally connected to the carburetor for applying a partial vacuum to thediaphragm 36 when the engine is in motion, thereby rotating the plate l2counter-clockwise as viewed in Fig- 1.

The invention utilizes any suitable source of vacuum, such as a pump(not shown), for supplying a controllable amount of suction to thediaphragm 35 by way of conduit 39. A vacuum indicator, such as themanometer 40, is connected to the conduit 39. The manometer may be ofany convenient type responsive to the range of vacua for which the sparkadvancing mechanism of the distributor I is designed.

According to the invention I provide a pair of relatively displaceableindicator members M, 42 for measuring the angle by which the plate I2 isrotated with respect to the housing ll. One of these members, e. g. thescale M, is secured to the movable plate l2, for example by means ofspring clips 43 engaging the condenser I9. The other member, e. g. thepointer 42, is held in fixed but adjustable position relative to thehousing II. For simplicitys sake I prefer to mount the pointer on thefree end of shaft [3 which remains stationary during tests carried outin accordance with the invention. The pointer is, for this purpose,provided with a spring clip M slidingly fitting over the end of theshaft and resiliently engaging same. As illustrated, the scale member 4!may be of generally sector-shaped configuration.

As will appear from the chart of Fig. 3, in which degrees of deflectionas read on the scale 4| are,

plotted against inches (or millimeters) of vacuum as read on themanometer 40, the deflection follows a non-linear law, represented bythe curve 45, which will be different for different types ofdistributors but will be predeterminable (usually in accordance withdata supplied by the manufacturer) for each particular type. pointer hasbeen set to zero position (by manually rotating it on the shaft l3) atzero vacuum, a gradually increasing vacuum is applied to the manometer60 and to the diaphragm 36, the deflections of pointer 42 on the scale4| being noted and compared with the values corresponding to curve 45.If the readings reasonably correspond to the predetermined values, nofurther action need be taken. If, however, there is a discrepancy, thedistributor is adjusted as follows:

A. low vacuum 121 is applied to the diaphragm, whereupon tension of thelight spring 29 is adjusted (by suitable manipulation of the pin 3|)until the pointer 42 shows the desired deflection dr- Next a highervacuum in is applied, whereupon the heavy spring 32 is adjusted (bysuitable manipulation of the pin 34) until the pointer '42 shows thedesired deflection 012. The vacua m, '02 are selected in those portionsof the range of op-' eration in which the heavy spring 32 and the lightspring 29 have, respectively, a negligible influence only upon thedeflection of the plate l2. Upon completion of these adjustments thereadings will generally correspond to the values of the chart, unlesseither or both springs are defective and must be replaced.

Reference to any external chart (such as the one shown in Fig. 3) may,however, be rendered unnecessary, at least for certain types ofdistributors, by providing the scale member 43 with one or more sets ofmarkings each permitting direct determination of the amount of vacuum atwhich a particular deflection should occur. Fig. 1 shows, by way ofexample, two such sets of markings, designated A and B, respectively;each of these relates to a particular type of distributor. The

first and the second marking of each set serves for the adjustment ofthe light and of the heavy spring, respectively, the third marking beingprovided for the purpose of counterchecking the performance of thesprings after adjustment has been made. This last marking may cover anangle of one degree or more, thus indicating a permissible tolerance.

It is to be understood that the invention is not limited to the specificform shown and described but that the arrangement illustrated may bemodified in various ways. Thus, for example, the scale member 4| may besecured to some portion of the breaker plate l2 other than the condenserl9. Also, the positions of the pointer and of the scale may be reversed,e. g. by making the scale portion of member 4! transparent so that thepointer 7 may be viewed therethrough. These and other After themodifications and adaptations will be readily apparent to those skilledin the art and are intended to be embraced within the scope of theinvention as defined by the appended claim.

I claim: I

A method of testing an automotive distributor of the vacuum-controlledtype by means of two relatively movable indicator members, the dis:

tributor including a shaft and a breaker plate rotatable independentlyof said shaft, which com prises the'steps of affixing one of saidmembers to the shaft, affixing the other of said members "to the breakerplate, placing said members in a predetermined reference positionrelative to'each, other by'rotating said one of said members on' theshaft with respect to the breaker plate, sue-1 cessively applyingdifferent amounts of vacuum to the distributor while holding the shaftstationary, and observing from the departure of said members from saidrelative reference position. whether the deflections of the breakerplate agree with standard deflections corresponding, respectively, tothe different amounts of vacuum.

PATTERSON O. STEWART.

No references cited.

